Work Piece Centering Device and Method of Broaching

ABSTRACT

A device for centering a work piece with respect to a centerline of a tool includes a radially-stationary component rigidly secured with respect to the tool such that the radially-stationary component and the tool are concentric. A biasing mechanism is biased away from the radially-stationary component to apply substantially equally-distributed radial force at a periphery of the work piece to thereby center the work piece with respect to the tool. A method of broaching a work piece having an inner and an outer diameter includes machining the outer diameter and then applying circumferentially-distributed radial force to the inner diameter or the outer diameter to thereby center the work piece with respect to a broach tool. After the applying step, the method includes broaching the inner diameter of the work piece using the broach tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/333,153, filed Jan. 17, 2006, and claims the benefit of U.S.Provisional Application No. 60/692,936, filed Jun. 22, 2005, both ofwhich are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The invention relates to a centering device for a work piece;specifically, a device that centers a work piece with respect to a tool,such as a broaching tool. The invention also relates to a method ofbroaching.

BACKGROUND OF THE INVENTION

The quality and performance of manufactured components is directlyrelated to conformance with part specifications. Conformance withspecifications, in turn, is affected by the number of manufacturingprocesses the component is subjected to, and the cumulative effect ofdimensional tolerance or “play” of different specifications. Internalgears, for instance, are typically formed, cut or otherwise providedwith an initial inner diameter bore and an outer diameter. Then thegears are subjected to an external broaching process at the outerdiameter and then an internal broaching process at the inner diameter.Because both of these processes are piloting operations, in which a worktool is directed axially through the component, specification tolerancesat the pre-broach inner diameter are tight to ensure a close fit withthe tool and minimize cumulative stack-up of dimensional errors. Infact, the diameter of the pilot section of the broach tool is typicallyonly 0.030 mm-0.050 mm under the smallest acceptable work piece innerdiameter. The need for tight dimensional tolerance increases componentcost. Additionally, after the external broaching process and prior tothe internal broaching process, the component is typically turned, i.e.,re-cut, at the inner diameter bore to ensure acceptable concentricity ofthe inner bore and newly-broached outer diameter. Significant capitalcost is associated with this additional process step. Workingperformance of the finished work piece will be enhanced and the numberof scrapped components will be reduced if concentricity of the innerdiameter, the outer diameter and the work tool can be controlled with aminimal number of process steps.

SUMMARY OF THE INVENTION

A centering device is provided that centers a work piece with respect toa broach tool to enhance concentricity and minimize the affect ofpositional tolerance stack-up on the finished component. Specifically,the centering device includes a radially-stationary component that isrigidly secured with respect to the tool so that the radially-stationarycomponent and the tool are concentric. The centering device alsoincludes a biasing mechanism (which may be a spring or a hydraulic orpneumatic piston) that applies a substantially equally-distributedradial force at a periphery of the work piece to center the work piecewith respect to the tool prior to machining the work piece with thetool. The periphery of the work piece at which the centering device actsmay be an inner diameter or an outer diameter. The outer diameter maybe, for instance, the diameter of the inner spline of external gearteeth. The centering device may center the work piece actively,utilizing hydraulic or pneumatic pressure, or passively, utilizing aspring or springs.

The centering device permits an improved method of broaching a workpiece. An outer diameter of the work piece may first be machined (e.g.,pot broached, castellated, hobbed or turned) to create a desiredconfiguration. The work piece is then shuttled to a broach tool and thetool is lowered so that a pilot section of the tool extends through thework piece. The centering device centers the work piece with respect tothe tool. The inner diameter of the work piece may then be broached bymoving the working portion of the tool axially across an innerperipheral surface of the work piece. No interim step of turning orrecutting the internal diameter of the work piece after machining theouter diameter is necessary.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an internal gear with externalsplines;

FIG. 2 is a partially cross-sectional elevational view of a centeringdevice for centering the inner diameter of a work piece with respect toa broach tool;

FIG. 3 is a fragmentary cross-sectional view of the centering device ofFIG. 2;

FIG. 4 is fragmentary cross-sectional view of a second embodiment of acentering device for centering the inner diameter of a work piece withrespect to a broach tool;

FIG. 5 is partially cross-sectional elevational view of a thirdembodiment of a centering device for centering the outer diameter of awork piece with respect to a broach tool;

FIG. 6 is a fragmentary cross-sectional view of the centering device ofFIG. 5;

FIG. 7 is a fragmentary cross-sectional view of a fourth embodiment of acentering device for centering the outer diameter of a work piece withrespect to a broach tool;

FIG. 8 is a fragmentary cross-sectional view of a fifth embodiment of acentering device for centering the outer diameter of a work piece withrespect to a broach tool;

FIG. 9 is a fragmentary cross-sectional view of a sixth embodiment of acentering device for centering the outer diameter of a work piece withrespect to a broach tool; and

FIG. 10 is a fragmentary cross-sectional view of a seventh embodiment ofa centering device for centering the outer diameter of a work piece withrespect to a broach tool.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, wherein like reference numbers refer to likecomponents, FIG. 1 shows a finished component 10 which is an internalgear processed to have splines 12 at an outer periphery and teeth 14 atan inner periphery. For quality control, it is important that theinternal teeth 14 are concentric with the outer splines 12. Othercomponents having similar concentricity requirements are internal gearswith castellated splines on the end or an external gear with an internalspline. The centering devices described below may be applied to workpieces for any component having a machined outer diameter (e.g., anouter diameter subjected to any known machining process such as potbroaching, castellating, hobbing or turning) and requiring a broachedinner diameter.

First Embodiment of a Centering Device

Referring to FIG. 2, an inner diameter centering device 16 (“IDcentering device”) is shown centering the as yet unfinished component ofFIG. 1 as a work piece, which will be referred to herein as 10′ in its'unfinished state. The ID centering device 16 ensures that the work piece10′ is centered with respect to a centerline 18 of a broaching tool 20prior to axial movement of the tool 20 to perform a broaching operationat the inner diameter 22 of the work piece 10′. The inner diameter 22 isachieved by a boring or turning operation occurring prior to theinternal diameter broaching operation. Preferably, the outer diameter 26of the work piece 10′, has already been subjected to a machiningoperation (e.g., pot broached, castellated, hobbed, turned, etc.), toform a machined surface having the external splines 12 of FIG. 1.Alternatively, within the scope of the invention, the outer diameterprocessing operation may have been to impart other surfacecharacteristics at an outer diameter of a work piece, such as externalteeth or axially-extending castellations.

The ID centering device 16 is annular, and circumscribes the pilotsection 19 of the tool 20. A retaining device 24 is fastened about thetool 20 and secures the ID centering device 16 to the tool 20 bysandwiching the device 22 in an axial position at a shoulder 27 formedon the tool 20. Thus, the centering device 16 will move axially with thetool 20 as the tool 20 is lowered through the work piece 10′ and thework section 29 of the tool 20 processes the surface at the innerdiameter 22. The retaining device 24 may be a split clamp, a wedge lock,a nut (as shown) with a ground thread or ground with retaining screws,or any other known means of retention that affords accurate location ofthe centering device 16 with respect to the tool 20.

Referring now to FIG. 3, the ID centering device 16 includes a basecomponent 30 and a retainer 32A, 32B having a top portion 32A and abottom portion 32B both of which are secured to the base component 30with fasteners 34. Each of the base component 30, the top portion 32Aand the bottom portion 32B are radially-stationary components, securedwith respect to the tool 20 and concentric therewith due to tighttolerances at which they are ground. If other types of retaining devicesother than a retaining nut are employed, concentricity may be ensuredby, for instance, a reliable locking device rather than tightdimensional tolerances. When secured to the base component 30, the topand bottom portions 32A, 32B are axially-spaced from one another to forma tapered slot 36 therebetween. A cavity 38 is defined by and formedbetween the base component 30 and the retainer portions 32A, 32B. Topand bottom wedging devices 40 and 42, respectively circumscribe the basecomponent 30 within the cavity 38. The wedging devices 40, 42 are sizedsuch that they are axially slidable within the cavity 38. It should beappreciated that the base component 30, the retainer 32A, 32B, and thewedging devices 40, 42 are all annular such that they circumscribe thetool 20.

Contact elements, which may be centering balls 44 (one shown) are nestedbetween the retainer 32A, 32B and the wedging devices 40, 42 and spacedabout the tool 20. A spring 46 (or a plurality of springs) is seatedbetween the base component 30 and the top wedging device 40. An annularwave spring or Belleville spring may be employed, or a plurality ofcompression springs may be circumferentially spaced about the tool 20within the cavity 38. The spring 46 biases the top wedging device 40toward the bottom wedging device 42. The wedging action of the spring 46imparts a radial force to the ball 44 via beveled surfaces 48, 50 of thewedging devices 40, 42, respectively, which contact the ball 44. Theball 44 is sized with respect to the slot 36 such that a portion of theball protrudes from the slot 36, spanning a clearance gap 52 (the sizeof which is a function of the dimensional tolerance of the work piece10′) between the inner diameter 22 (see FIG. 2) and the tool 20. Thus,the ball 44 is biased by the spring 46 and the wedging devices 40, 42 tocontact and impart a radially-outward force at the inner diameter 22 ofthe work piece 10′. Because a plurality of balls 44 circumscribes thetool 20, the radially-outward force is equally distributed about theinner periphery 54 of the work piece 10′ and acts in an axial plane P onthe work piece 10′. Thus, the base component 30 acts as a reactionmember for the radial force imposed by each the ball 44 at the innerperiphery of the work piece 10′. The centering balls 44, wedging devices40, 42 and spring 46 may be referred to as a biasing mechanism.

Because the base component 30 is concentric with the tool 20, the innerdiameter 22 of the work piece 10′ is made concentric with the tool 20,eliminating tolerance stack-up between the tool 20 and the innerdiameter 22. Once the work piece 10′ is made concentric with the tool20, a top clamp 56 is moved downward to secure the work piece 10′between the top clamp 56 and a part locator 58, such as a work table.Accordingly, a subsequent broaching operation at the inner diameter 22may be carried out without an intervening turning operation to ensureconcentricity of the inner diameter 22 to the tool 20. Because the tool20 is concentric with the work piece 10′, the tooth form or featureimparted by the tool 20 will be concentric with the inner diameter 22.

Second Embodiment of a Centering Device

FIG. 4 shows an alternative embodiment of an inner diameter (ID)centering device 116 which in this case is integrated with a broach tool120. The centering device 116 centers a work piece 110′ with respect toa centerline 118 of the tool 120 prior to an internal broachingoperation. The work piece 110′ has already been subjected to a machiningoperation, such as pot broaching, to form splines at an outer diameter126. The ID centering device 116 includes a retainer 132A, 132B having atop portion 132A and a bottom portion 132B both of which are secured tothe tool 120 with fasteners 134. Production clearances of the tool andthe centering device ensure concentricity of these components withrespect to one another. The top portion 132A and the bottom portion 132Bare radially-stationary components, secured with respect to the tool 120and concentric therewith. When secured to the tool 120, the top andbottom portions 132A, 132B are axially-spaced from one another to form atapered slot 136 therebetween. The tool 120 is formed with a beveledsurface 148. A cavity 138 is formed between the tool 120 and theretainer 132A, 132B. A wedging device 142 circumscribes the tool 120 andis sized so that it is axially slidable with respect to the tool 120 inthe cavity 138 between the bottom portion 132B and a shoulder 143 of thetool 120 adjacent the beveled surface 148.

Contact elements, also referred to as centering balls 144 (one shown)are nested between the retainer 132A, 132B, the beveled surface 148 andthe wedging device 142. A spring 146 (or a plurality of springs) isseated between the retainer bottom portion 132B and the wedging device142. An annular wave spring or Belleville spring may be employed, or aplurality of compression springs may be circumferentially spaced aboutthe tool 120 within the cavity 138. The spring 146 biases the wedgingdevice 142 toward the beveled surface 148. The wedging action of thewedging device 142 and the beveled surface 148 imparts a radial force tothe ball 144. The centering balls 144, wedging device 142 and spring 146may be referred to as a biasing mechanism. The ball 144 is sized withrespect to the slot 136 such that a portion of the ball 144 protrudesfrom the slot 136, spanning a clearance gap 152 between the innerdiameter 122 of the work piece 110′ and the tool 120. Thus, each ball144 imparts a radially-outward force at the inner diameter 122 of thework piece 110′. Because a plurality of balls 144 circumscribes the tool120, the radially-outward force from the balls 144 is equallydistributed about the inner periphery 154 of the work piece 110′. Theball 144 rests against the beveled surface 148 of the tool 120 and thusmakes the inner diameter 122 of the work piece 110′ concentric with thetool 120. Once the work piece 110′ is made concentric with the tool 120,a top clamp 156 is moved downward to secure the work piece 110′ betweenthe top clamp 156 and a part locator 158, such as a work table.Accordingly, a subsequent broaching operation at the inner diameter 122may be carried out without an intervening turning operation to ensureconcentricity of the inner diameter 122 to the tool 120. Because thetool 120 is concentric with the work piece 110′, the tooth form orfeature imparted by the tool 120 will be concentric with the innerdiameter 122.

Third Embodiment of a Centering Device

Referring to FIG. 5, a third embodiment of a centering device 216 which,in this case, is an outer diameter (“OD”) centering device, is showncircumscribing a work piece 210′ and a broach tool 220. The centeringdevice 216 is rigidly secured to a top clamp 256 which is concentricwith respect to the broach tool 220. Alternatively, but not shown, thecentering device 216 may be secured to a part locator 258 which may be atable or another machine component. Such a design would work equally aswell as securing the centering device 216 to the clamp 256, as both theclamp 256 and the part locater 258 are concentric with respect to thetool 220. (Concentricity of the tool 220 with respect to the centeringdevice 216 is ensured by an adjustment feature 235 (shown and describedbelow with respect to FIG. 6)).

Referring to FIG. 6, the centering device 216 acts on an outer periphery255 of the work piece 210′ at the outer diameter 226 (the outer diameter226 is the inner diameter of the spline formed the outer diameter of thework piece 210′) to center the work piece 210′ with respect to acenterline 218 (see FIG. 5) of the tool 220.

The OD centering device 216 includes a base component 230 and a retainer232A, 232B, 232C having a top portion 232A and a bottom portion 232B(both of which are secured to the base component 230 with fasteners 234)as well as a cover plate 232C. Each of the base component 230, the topportion 232A and the bottom portion 232B are radially-stationarycomponents, secured by the adjustment feature 235 with respect to aclamp 256. The adjustment feature 235, commonly referred to as a“stir-around” adjustment feature, allows manual, radial adjustment ofthe position of the centering device 216 with respect to the clamp 256to ensure proper centering of the centering device 216 with respect tothe centerline 218 of the tool 220. The adjustment feature 235 may be ajack screw. Various methods of alignment, such as by laser, may beemployed to ensure concentricity of the centering device 216 with thetool 220, the adjustment feature 235 being employed to achieve thedesired alignment. When secured to the base component 230, the top andbottom portions 232A, 232B are axially-spaced from one another to form aslot 236 therebetween. A cavity 238 is formed between the base component230 and the retainer 232A, 232B. Top and bottom wedging devices 240 and242, respectively circumscribe the retainer 232A, 232B within the cavity238. The wedging devices 240, 242 are sized such that they are axiallyslidable within the cavity 238. The base component 230, the retainer232A, 232B, and the wedging devices 240, 242 are all annular such thatthey circumscribe the tool 220 (shown in FIG. 5).

Centering balls 244 (one shown) are nested between the retainer 232A,232B and the wedging devices 240, 242. A spring 246 (or a plurality ofsprings) is seated between the base component 230 and the top wedgingdevice 240. An annular wave spring or Belleville spring may be employed,or a plurality of compression springs may be circumferentially-spacedabout the tool 220 within the cavity 238. The spring 246 biases the topwedging device 240 toward the bottom wedging device 242. The wedgingaction caused by the spring 246 imparts a radially-inward force to theball 244 via beveled surfaces 248, 250 of the wedging devices 240, 242,respectively, which contact the ball 244. A plurality of centering pins260 (one shown) (also be referred to as contact elements) is placedradially-inward of the balls 244 in the cavity 238. A shoulder portion262 of the pin 260 is larger than the slot 236 such that the pin 260 isretained by the top and bottom portions 232A, 232B. A head portion 264of the pin 260 is sized to protrude from the slot 236 whenradially-inward force from the ball 244 acts upon the pin 260. Annularseal 265 between the head portion 264 and the top and bottom portions232A, 232B prevents debris from entering the cavity 238 to ensure theaccuracy of the centering device 216. The head portion 264 contacts theouter periphery 255 of the work piece 210′ at the outer diameter 226(which is the inner diameter of the splines at the outer periphery 255).Thus, the pin 260 imparts a radially-inward force at the outer diameterspline 226 of the work piece 210′. Because a plurality of balls 244 andpins 260 circumscribe the work piece 210′, the radially-inward force isequally distributed about the outer periphery 255 of the work piece210′. Thus, the base component 230 acts as a reaction member for theradial force imposed through the balls 244 and pins 260 at the outerperiphery 255 of the work piece 210′. The centering balls 224, the pins260, the wedging devices 240, 242 and the springs 246 may be referred toas biasing mechanism. Because the base component 230 is concentric withthe tool 220, the outer periphery 255 of the work piece 210′ is madeconcentric with the tool 220, eliminating tolerance stack-up between thetool 220 and the outer diameter 226. Accordingly, a subsequent broachingoperation at the inner diameter 222 of the work piece 210′ may becarried out without an intervening turning operation to ensureconcentricity of the inner diameter 222 to the outer diameter 226,because the outer periphery 255 of the work piece 210′ is centered withrespect to the tool centerline 218.

Fourth Embodiment of a Centering Device

Referring to FIG. 7, an alternative embodiment of an OD centering device316 is depicted. Like the embodiment of FIG. 6, a retainer 332A, 332B,332C having a top portion 332A, a bottom portion 332B and a cover plate332C is secured to a clamp 356. The top portion 332A, bottom portion332B and cover plate 332C are radially-stationary components. Theposition of the centering device 316 with respect to the clamp 356(which is centered with respect to a broach tool (not shown)) may beadjusted with an adjustment feature 335. A plug 366 retains a spring 346in a cavity 338 to bias the head portion 364 of a centering pin 360partially through a slot 336 formed between the top and bottom retainerportions 332A and 332B and into contact with the outer periphery 355 ofa work piece 310′ at an inner diameter of a spline formed thereon. Aplurality of springs 346 is spaced circumferentially about the workpiece 310′, as are centering pins 360. Plug 366 may be a single annularplug or may represent a plurality of circumferentially-spaced plugs.Seals 365 prevent debris from entering the cavity 338 to ensure theaccuracy of the centering device 316.

Fifth Embodiment of a Centering Device

Referring to FIG. 8, another embodiment of an OD centering device 416 isillustrated. The centering device 416 functions the same as centeringdevice 216 of FIG. 6, except that no centering pin is utilized; instead,a slot 436 formed by the top and bottom retainer portions 432A, 432B istapered to allow a contact element or centering ball 444 to contact theouter diameter 426 of a work piece 410′ for centering the work piece410′. A plurality of balls 444 is located about the work piece 410′. Aspring 446 maintains tension on top and bottom wedging devices 440, 442,to retain the ball 444 against the work piece 410′. The spring 446,centering balls 444 and wedging devices 440, 442 may be referred to as abiasing mechanism. The embodiments of FIGS. 2-8 are “passive” centeringdevices in that the stored potential energy of a spring (i.e., spring46, 146, 246, 346 or 446) automatically accomplishes the centeringfunction.

Sixth Embodiment of a Centering Device

Referring to FIG. 9, another embodiment of an OD centering device 516 isillustrated. A base component 530 and a retainer 532 are secured to aclamp 556 via an adjustment feature 535 which is centered with respectto a broach tool (not shown). The base component 530 and the retainer532 are both radially-stationary components. The position of thecentering device 516 may be adjusted with the adjustment feature 535.Channels 570A, 570B provided in the base component 530 allow externallysupplied and controlled hydraulic or pneumatic hydraulic or pneumaticpressure to be applied to a piston 572, which is forced axially downward(if greater pressure is applied in channel 570A) to act as a wedgingdevice to tighten a contact element or a collet 574, or upward (ifgreater pressure is applied in channel 570B) to loosen the collet 574which contacts a splined outer periphery 554 of a work piece 510′ at anouter diameter of the work piece 510′ (which is an inner diameter of thespline thereon). The piston 572 and collet 574 may be referred to as abiasing mechanism. Seals 565 are employed to prevent dirt and debrisfrom contact the working parts of the centering device 516. Unlike thepreviously described centering devices 16, 116, 216, 316 and 416, thecentering device 516 is an “active” centering device. An “active”centering device is one in which the application of radial force is notautomatic (as with a spring force) but must be selectively applied.Because hydraulic or pneumatic pressure is used to create theradially-inward force on the piston, much higher forces retain the workpiece 510′ in a centered position than are available with designsutilizing spring force. In addition the amount of the centering forcecan be varied or removed during the cutting stroke of the broach tool.

Seventh Embodiment of a Centering Device

Another embodiment of an active OD centering device 616 is illustratedin FIG. 10. A base component 630 and a retainer 632A, 632B having a topportion 632A, a bottom portion 632B are secured to a clamp 656 which iscentered with respect to a broach tool (not shown) via an adjustmentfeature 635. Channels 670A, 670B in base component 630 allow externallysupplied or controlled hydraulic or pneumatic pressure to be applied toa piston or wedging device 640 which is forced axially either downward(if greater pressure is applied in channel 670A) or upward (if greaterpressure is applied in channel 670B), applying force to a contactelement or centering ball 644 (one shown but a plurality beingdistributed about the work piece 610′) via a beveled surface 648 whichacts with beveled surface 650 of wedging device 642 to cause thecentering ball 644 to protrude from slot 636 formed between the top andbottom portions 632A, 632B into contact with an outer periphery 654 atthe inner diameter of the spline formed on work piece 610′. Seals 665are employed to prevent dirt and debris from contact the working partsof the centering device 516. The base component 630 and retainer 632A,632B are radially-stationary. The wedging devices 640, 642 and ball 644may be referred to as a biasing mechanism.

By employing any of the centering devices described above with respectto FIGS. 1-10, a work piece having a broached outer diameter may becentered with respect to a centerline of a broaching tool. The centeringfunction of the centering device enables the broaching tool to be usedto broach the inner diameter of the work piece without turning the innerdiameter to be concentric with the outer diameter between machining theouter diameter and broaching the inner diameter.

A method of broaching a work piece having an inner diameter and an outerdiameter will now be described with respect to the structure andembodiments described above. However, the method may also be performedwith other embodiments of centering devices than those described above.The method includes machining the outer diameter of the work piece. Forinstance, the work piece 10′ of FIGS. 2 and 3 has a splined outerdiameter such as is shown with respect to the work piece 10 in FIG. 1.The outer diameter may be machined in a number of ways including potbroaching, castellating, hobbing or turning.

The method also includes applying circumferentially-distributed radialforce to the inner diameter 22 or the outer diameter (such as outerdiameter 226 of FIG. 6) of the work piece to thereby center the workpiece with respect to a broach tool such as tool 20 in FIG. 2 (when thework piece is centered from the inner diameter) or tool 220 of FIG. 5(when the work piece is centered from the outer diameter). After theradial force is applied, the method includes broaching the innerdiameter 22 of the work piece using the broach tool 20 that work piecehas been centered with respect to (broach tool 220 in an embodimentusing an outer diameter centering device such as in FIGS. 5 and 6).Because the work piece is centered with respect to the tool under themethod, the method may avoid a step of turning the inner diameter to beconcentric with the outer diameter after the outer diameter is machinedbut before the inner diameter is broached.

Under the method, a centering device may be used to apply thecircumferentially distributed radial force of the work piece. In thatinstance, the method includes centering the centering device withrespect to the broach tool. This may be accomplished, for example, byadjusting the stir-around feature such as stir-around feature 235 shownin FIG. 6, as described above.

If the centering device is a passive centering device, such as in theembodiments described in FIGS. 2-8, the step of applyingcircumferentially distributed force to the work piece occursautomatically when the centering device is aligned with the work piece.The aligning may occur when the tool (such as tool 220) is lowered sothat the centering device circumscribes the work piece (as the centeringdevice 216 circumscribes the work piece 210′ in FIG. 6) or such that thework piece circumscribes centering device (as the work piece 10′circumscribes the centering device 16 in FIG. 3). Preferably, the methodincludes axially clamping the centered work piece prior to the step ofbroaching the inner diameter. For instance, in the embodiment shown inFIG. 3, the clamp 56 is applied to retain the position of centered workpiece 10′ prior to broaching the inner diameter of the work piece 10′with the broaching tool 20.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A method of broaching a work piece having an inner diameter and anouter diameter comprising: machining the outer diameter; applyingcircumferentially-distributed radial force to the inner diameter or theouter diameter of the work piece to thereby center the work piece withrespect to a broach tool; and after the applying step, broaching theinner diameter of the work piece using the broach tool.
 2. The method ofclaim 1, wherein the method is characterized by an absence of turningthe inner diameter to be concentric with the outer diameter after themachining step and before the broaching step.
 3. The method of claim 1,wherein the applying step occurs automatically as a result of axiallyaligning a centering device with the work piece.
 4. The method of claim1, further comprising: centering a centering device with respect to thebroach tool, wherein the radial force is applied by the centeringdevice.
 5. The method of claim 4, further comprising: prior to saidapplying step, axially aligning the centering device with the workpiece.
 6. The method of claim 1, wherein the machining step is one ofpot broaching, castellating, hobbing or turning.
 7. The method of claim1, further comprising: after the applying step, clamping the centeredwork piece prior to the broaching step.